SCHMITT TRIGGER (Hysteresis) Circuit
Can also be called AN INVERTER or a SCHMITT INVERTER
We have animated the circuit to show how the output goes high
or low according to the input level. The animation shows a wide gap
between the input levels when the time when the output goes HIGH or
LOW and this gap is called the HYSTERESIS GAP.
This circuit is called a SCHMITT TRIGGER and it is used in many
building-blocks (using a different chip - such as 74c14) to prevent false triggering.
It prevents false triggering because as the input rises, the output
does not change until the input voltage is fairly high. If the input
voltage falls, the output does not change until the input falls
about 30%. This means small fluctuations (noise) on the input
do not have any effect on the output. The output is the INVERSE of
the input - in other words the 555 is a SCHMITT INVERTER. The second
diagram shows a Schmitt Trigger building block.
SCHMITT TRIGGER BUILDING BLOCK
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